You may have read by now about the retired Royal Canadian Mounted Police officer who has invented the “pot breathalyzer.” It’s the inevitable and predictable response to our years of demanding that we “regulate marijuana like alcohol.” Despite the fact that driving while impaired on cannabis has been illegal in all 50 states ever since people began getting impaired on cannabis, the framing of “treat it like alcohol” demands that we do just that and implement a roadside technology for police officers to determine who is too high to drive.

Yes, “treat it like alcohol” was a helpful analogy to get people for whom “legal marijuana” was an abstract fantasy to a place where they could understand that regulation of a social drug is preferable to its prohibition. People were familiar with legal alcohol and all its ramifications and people could remember prohibition of alcohol and all its negatives. So “treat it like alcohol” helped them to understand that there could be a regulatory system that would be better than prohibition when it comes to marijuana. It’s likely that marijuana legalization would not have passed as soon as it did without the “marijuana is safer than alcohol” and “regulate marijuana like alcohol” analogies.

The problem with the analogy is that marijuana and alcohol are not analogous. Alcohol is a toxic, hydrophilic (water-soluble) molecule with a verifiable, dose-dependent ability to impair its user on a weight-related basis. Given 100 persons of weight X who drink amount Y, their resulting blood-alcohol content (BAC) will be a fairly consistent indicator of their physical and mental impairment. Sure, you might get one or two outliers, like the obese alcoholic with a massive tolerance or the petite abstainer who’s drunk once a year on a glass of champagne on New Years’ Eve, but for the vast majority, a BAC of 0.08 or above is a very strong indicator they’re too drunk to drive.

On the other hand, the THC in cannabis is a non-toxic, lipophilic (fat-soluble) molecule that affects every user differently and even affects the same user differently depending of many factors. You can’t guarantee with any accuracy that someone with, say, a reading of 5ng of active THC per milliliter of blood is going to be too impaired to drive. Some long-term marijuana users may awaken after eight hours of sleep with levels above 5 ng. Many marijuana users won’t even exhibit signs of roadway impairment at levels above 20 ng or even 50 ng, as demonstrated by Seattle news station KIRO’s experiment with three marijuana users of varying degrees of use and tolerance.

The pot breathalyzer fulfills law enforcement’s desire for a simple “bright line” magic number that allows them to arrest drivers for marijuana use. Its inventor explains that the current model can only detect the THC in the lungs that is indicative of use within the past two hours. That would be perfect for most of the states, he explains, that have so-called “zero tolerance” for marijuana use by drivers, where the detection of any amount of THC means the state has proved the driver was impaired. He also intends to improve the technology to determine amount of THC to handle states like Washington and Colorado that have imposed a 5 ng limit.

But the pot breathalyzer still does not tell us anyone behind the wheel was too impaired to drive, it just tells us they had used marijuana recently. That, I fear, will evolve to become the new standard for marijuana users behind the wheel. It won’t be a matter of how impaired we are behind the wheel, it will just matter how soon we’ve gotten behind the wheel. 

It seems to me quite discriminatory when we hold no such requirement for alcohol users. Can you imagine the uproar if someone suggested a law where drinking a single beer meant an automatic two hour “no driving” requirement? Under current law, I, as a 240lb man, could slam five shots of tequila in 20 minutes and immediately get behind the wheel, but my 0.076 BAC would not by itself prove I was too impaired to drive.

If we’re really going to “treat marijuana like alcohol,” we need to emphasize that the way we treat alcohol-using drivers is by proving someone is too impaired to drive by their body chemistry. That’s something even the US National Traffic Highway Safety Commission to this day still says is “inadvisable” to try to determine with marijuana consumption. Why don't we just continue to treat marijuana drivers the way we have been for decades, by proving they're too impaired to drive by observation and roadside sobriety tests? It's not as if marijuana legalization invents marijuana and cars -- we've already been dealing with this quite successfully.

"Radical" Russ Belville is the host of The Russ Belville Show, which airs live at 3pm Pacific.